1. Field of the Invention
The present invention relates to a communication control method and the apparatus in a mobile communication system. More particularly, the present invention relates to a communication control method used for controlling communication between base stations and mobile stations on the basis of SDMA: Space Division Multiple Access in a mobile communication system.
2. Description of the Related Art
Conventionally, a communication control method of space division multiple access (which will be called SDMA hereinafter) is proposed. When adopting SDMA as a communication control method between the base station and the mobile station in a mobile communication system using cellular system, as shown in FIG. 1 for example, each of base stations 201, 202, 203 which control communication areas (cells) E1, E2, E3 respectively forms a radio wave beam B which extends to a direction where the mobile station exists instead of radiating radio wave which covers the whole communication area for communicating with the mobile station.
In the cellular mobile communication system in which communication control between the base station and the mobile station is performed according to the communication control method of SDMA, when directions from the base station to the mobile stations are different, directions of radio wave beams B which are formed are different. Therefore, it becomes possible to perform communication in adjacent areas by using the same frequency so that it can be expected that frequency use efficiency in the directions of horizontal plane improves.
However, as the number of the mobile stations residing in a communication area of each base station increases, cases where radio wave beams are formed in the same direction or in the opposite direction in a plurality of adjacent areas in the same timing or cases where radio wave beams formed to a plurality of mobile stations from the base station overlap increase so that the radio wave beams interact each other as interference waves.